Use of a peroxy bleaching agent in washing, such as hydrogen peroxide etc., belongs to known technology. This peroxy bleaching agent is used at high temperatures and can bleach stains with tea, coffee, wine, fruit etc. However, the bleaching effect of the peroxy bleaching agent is significantly lowered at 60° C. or less, and therefore, use of a transition metal complex having an ability to activate bleaching in combination with the peroxy bleaching agent has been examined; for example, JP-B 7-65074 discloses a manganese complex with cyclic polyamine as a ligand, JP-A 11-507689 discloses a cobalt ammine complex, JP-A 8-67687 and JP-A 11-515049 disclose a Schiff base derivative complex of manganese or cobalt, and WO-A 95/34628 and WO-A 97/48710 disclose an iron complex with a pyridyl methylamine derivative as a ligand. However, these complexes fail to achieve a sufficient bleaching effect on polyphenol-based stains such as stains with tea, and bring about problems such as decolorization of dyes and damage to fibers.
It is important for a factor for allowing a transition metal complex-containing bleaching composition to exhibit a bleaching activity that the complex itself is stable in the form of an aqueous bleach solution, and upon reacting with a hydrogen peroxide source, forms a certain kind of oxidized active species to react with stains. In addition, whether or not the catalyst can approach a subject of bleaching (fibers (cloth) and rigid surfaces of glass, pottery etc.) is also mentioned as another important factor. Both the subject of bleaching and a majority of stains are negatively charged (anionic), and the peroxides such as hydrogen peroxide sources are also anionic, but for preferable electrostatic interaction, it is advantageous that the catalyst itself is cationic (JP-A 1-97267). Actually, the manganese complex described in JP-B 7-65074 and the cobalt complex described in JP-A 11-507689 are designed to be cationic complexes so as to easily approach fibers (cloth). However, the bleaching compositions containing such complexes have problems such as decolorization of dyes and damage to fibers as described above.
On the other hand, a large cyclic tetramide transition metal complex described in WO-A 98/03625 is excellent in an ability to bleach a wide variety of stains with tea, wine, fruit etc. in aqueous solution, but is poor in an ability to bleach stains adhering to a cloth. An estimated reason for this insufficient ability is that this complex is anionic and thus hardly approaches a negatively charged cloth.
Further, WO-A 98/58735 discloses a compound having a pyridine skeleton, and WO-A 99/64156 discloses a compound having a pyridinium ring, but these compounds are different in structure from the compound of the present invention, and do not exhibit an excellent effect achieved by the present invention.